Motor-control apparatus



Sept. 4, 1928. 1,683,210

I c; c. RUNNER MOTOR con'moug. APiARATUs Filed Aug. 6, 1925 lZOm Inventor 1 Claude C. Qunhen' Hts Attorney.

Patented Sept. 4.192s.

IUNlTED' STATES CLAUDE O. RUNNER,

PATENT orrlca OF SOHENEG'IADY, NEW YORK, ASSIGNOB TO GENERAL ELEUI'RIG:11am, A. CORPORATION 01' NEW YORK.

' uoron-comndr. Arranurus.

Application filed Augult My invention relates to the control of electricmotors and provides improved control apparatus for connecting the motorsto a source ofcurrent and automatically limiting I the current of themotors during the starting period.

Although well adapted for controlling a single motor of a type thatrequires limitation of the motor starting current, the control apparatusembodying the present invention is particularly advantageous in.controlling a plurality of motors which it is desired to startsuccessively with the starting current of each motorof limited value. Bymeans of the present invention the starting current of each of aplurality of motors may be limited by a single current limitingresistor.

In carrying the invention into efiect in a control system for aplurality of motors, a separate line switch is provided for connectingeach motor to a source of supply and in accordance with the preferredform of the invention, a current llmlting resistor is con-- 2 nected inthe circuit through which all the -motors are supplied with current. Thecurrent limiting resistor is normally short circuited by a switch whichis arranged to be operated so as to insert the resistance in the motorcircuit prior to operation of each of the motor line switches thusinsuring that the starting current oi each motor .is of limited value. Atime element device automaticallycontrols the resistor short circuitingswitch in such manner that the short circuit around the current limitinresistor is reestablished a predetermined time interval after eachinsertion of the resistor in the motor circuit. Y

Although not necessarily limited thereto, the present invention is welladapted for controlling a group of motorsdriving amachine such. forexample, as a multi cutter head woodworking machine. Where-the control 5apparatus, as well as the driving motors, is mounted upon the drivenmachine my-invem tion permits a considerable reducti'on in the spacerequired for the controlling apparatus. Inthe accompanying drawing thesingle vfigure is a schematlc diagram of a control system'embodyingmyinventionv in a form suitable for controllinga plurality of electricmotors... The control. system illustrated is designed for controllingthe several driving s, 1925. Serial m. 48,638.

motors of a multi cutter head woodworking machine. Referring to'thedrawing, the electric drivmg motors 10, 11 and 12, are shown as of thethree phase alternating current induction type, although the presentinvention maybe applied with equal advantage to control other in detailin the drawing, it will be understood that each of the motors 10, 11 and12 may be connected to drive one of the cutting heads of a multi headwoodworking machine.

The group of electric motors comprising the.

motors 10, 11,12 is arranged to be supplied with power from either thelow frequency supply lines L or the hi h frequency supply pes of motors.While not shown lines L through a suita 1e selective switch A 13. Theelectroresponsite line switches 14,

15 and 16 are provided for connecting the motors 10, 11 and 12respectively to either supply lines L or L depending upon the previousoperation of the selective switch 13.

In order to limit the current supplied to each of the motors 10, 11, 12,during the starting period, the current limiting resistors 47 areconnected in the circuit through which the motors are supplied withpower and the electroresponsive switch 18 is provided for shortcircuiting the resistors47 during normal operation of the motors.

In accordance with the present invention the electroresponsive switch 18which controls the short circuit around the currentlimiting resistors 47is normally closed so as to short circuit the resistors 47 before andduring operation of an one of the group of motors 10, 11, 12. us whenthe switch 18 is of the type which is operated to the closed positionupon en'er' 'zation of the operating winding thereo as shown in thedrawing, the operating winding of the switch is connected so as to beenergized before, as well as during, the operation of any of the grou ofmotors 10, 11, 12, as will be more mi} the operation of the controlsystem illustrated. It will be understood, however, that if desired theresistance controlling switch 18 may be of the type which is normallybiased to the closed position, and operated t5 the open position'uponthe energization of the operating winding. In either case suitable timeelement means are provided for maintaining the short circuit around thedescribed in connection with and assigned to the assi nee o resistors 47open for a predetermined time interval.-

In the arrangement shown a time element relay 19 of the type fullydescribed and broadly claimed in Patent No. 1,638,372, issued August 9,1927 to George E. Stack, my present invention, is provided orcontrolling the switch 18. As will be more fully described hereinafter,the time element control arrangement is such that the current lim1t1ngresisters47 are maintained inserted in the circuit throu h which poweris supplied to the group motors 10, 11 and 12 vfor a predetermined timeinterval during the startin of each motor in the group.

It Wlll be seen that the time element relay 19 is provided with awinding 20 for o crating the normally open contact 21 to t e closedpositionland the winding 22 serves to retard the o eration of thecontact 21 by periodically ho ding and releasing the movable magneticmember 23 when energized from an alternating current source. I wouldhave it understoo however, that my present invention is not limited toany particular type of time delay means for controlling the operation ofthe resistance short circuitinglswitch 18.

otors 24 and .25 also are shown as of the three phase alternatingcurrent type and are mechanically shown in the drawing to individuallydrive a cutting head of the woodworking machine.

, The motors .24 and 25 are arranged to be supplied with ower only fromthe low frequency supply ines L, and these motors are of such a sizethat they may be connected directly to the su ply lines upon operationof the correspon ing electroresponsive line switches 26 and 27.

It will be observed that the electric motors 10,11, 12, 24, 25 areprotected by means of the thermal responsive devices 28, 29, .30,

31,32, respectively, each of which is connected to be heated inaccordance with-the.

switches 14, 15 and 16 respectively, and,

thereby control the starting of the corresponding motors 10, 11, 12. aThe line switches 26 and 27 of the corresponding motors 24 and 25are'controlled by the manu- -al1 operated push buttons or masterswltches' 36 and 37 respectively. It will be seen that the motorstarting push buttons 33, 34, and 36, are of the two-position typehaving both upper and lower contacts, and are normally biased intoengagement ep'nnected by means not tacts are closed. The'stopping of allof 74 the motors 10, 11, 12, 24 and 25, is controlled by the normallyclosed push button 38, as well as by the undervoltage protective relay39, which is energized responsively to the voltage impressed upon thegroup of 7:

motors 10, 11 and 12 as shown in the drawing. The motor 25 may bestopped separately by operation of the pormally closed push button 40.

The operation of the control system illus- 8 trated is as follows: Withthe supply line L energized from a suitable alternatm current source ofsuitable frequency, sue for example, as cycles, and the supply lines Lenergized from an alternating current 8 source of a relatively higherfrequency such, for example, as cycles, the selective switch 13 may beoperated to sup ly power to the oup of motors 10, 11- an 12, from eithert e supply lines L or the su ply lines 9 L This permits the cutter hea sof the woodworking machine to be driven by the motors 10, 11, 12 ateither low speed or high speed, I depending upon the nature of theicutting operation, as well as the nature of 9 the wood bein operatedupon.

Assuming t at the selective switch 13is operated to its lower positionto operate the group of motors 10, 11 and 12, from the igh frequencysupply lines L,, the under- 1 voltage responsive relay 39 then isenergized by the voltageacross one phase of the suply lines L and ocrates to the circuit closmg position. T1115 at once establishes anenergizing circuit for the operating winding 1 20 o the time elementrelay 19 which may be traced from the right hand supply line L throughthe conductor 41, the contacts of the several termal overload rotectivedevices 28, 29, 30, 32 and 31, and t ence through 1 the contact of the'undervoltage relay 39, the normally closed push button 38, the uppercontacts of the several motor starting push buttons 33, 34 and 35, theconductor 42, the operatin windin 20 and the conductor 1 43 to the midle supp y line L,. The resultmg energlzation' of the operating winding20 starts operation of the contact 21 to the closed position. At thesame time, the retardlng winding 22 of the time element re- I lay 19 andthe operating winding of the res1stance controlling switch 18 areenergized n parallel circuit with the operating windmg 20. v It will beobserved that the retarding wlndmg 22 and the operating winding ofswitch 18 are energized in series circuit. In thls way the resistance ofthe retarding w1ndmg22 serves to limit the current passmg through theoperating winding of switch 1 18 to a-value which is in'sufiicient toefiect operation ofthe switch 18 to the closed'position. However, thecurrent passin through the retardi'n to peri'odica g 23 and there inding22 is of suflicient value attract ,the magnetic member delay theoperation of the contact 21 to t e'closed position for a prede-,

termined time interval. When the contact 21 is closed the retardingwinding 22 is short operated tothe closed position to short cirthroughthe conductor 41, contacts of the cuit the current limiting resistors47.

With the .switch 18 thus operated to its initial osition in which thecurrent limiting resistors 47 are short circuited any one of the motorstarting push buttons 33, 34, 35, may be operated .to set thecorresponding motors 10, 11, 12, into operation, although it will beobserved that the push button starting switches are interlockedelectrically so' that onlya single motor can be started at any one time.

If the motor 10 is to be started first, the starting push button 33 isdepressed. As the push button 33 disengages its upper contacts theenergizing circuit throu h the conductor 42 for the operating win ing ofthe resistor controlling switch 18 is interrupted and switch 18immediately opens to insert the current limiting resistor 47 in thecircuit prior to the connection of the motor 10 thereto. As the pushbutton 33 engages with its lower contacts an energizing circuit for lineswitch 14 is established extending thermal devices 28 to 32, theundervolta e relay 39, the normally closed stop pus h button 38, thepush button 33 in its lower position, the operating winding of lineswitch 14, and the conductor 43. The resultmg closure of line switch 14simultaneously establishes a holding circuit through the auxiliarycontact 44 with which the switch 13 provided and connects motor 10' tothe supply lines L, with the current limiting resistors 47 in the motorcircuit. The motor 10 at once starts and soon accelerates to normalrunning speed, the starting and the accelerating current of the motorbeing limited to a suitable value by the resistors 47.

When the uppercontacts of the-push button 33 were opened to deenergizethe switch 18 and thereby inserting the resistors 47 in the motorcircuit, the operating winding 20 of the time element relay 19 also wasdeenergized, thus permitting the contact 21 to immediately return to theopen position in which it is shown. However, as soon as the resistancecontrolling switch 18 is opened, the winding 20 at once is reenergizedthrough the auxiliary contact 45 with which the switch 18 is provided.Thus, upon the opening of'the switch 18 to insert the resistors in themotor circuit, the contact 21 of thetime element rela 19 immediately isset into operation to t e closed osition to reenergize the operating wining of switch 18 after terval.

- In case the. motor-starting push button 33 a predetermined time inisnot released so as to close its upper contacts before the contact 21 ofthe time element relay 19 is operated to the closed position, the switch181 is energized only .18 at recurring interva s.

However, when the motor startingpush.

button 33 is released as soon as the motor 10 is started and before thetime element relay 19 operates to close its contact 21, as/will be thecase under all ordinary operating conditions, the switch 18 ismaintained in the open position only for the time interval required foroperation of the relay 19. This is dueto the fact that the push button33 in its upperposition maintains the operating winding of switch 18energized through a circuit which is in shunt circuit with the auxiliarycontact 45 of the switch 18. Thus, under normal operating conditions theswitch 18 and the time element relay 19 function to maintain the currentlimiting resistors- 47 effective to limit the current of the motor foronly a predetermined time interval after the motor is connected to thesource of supply.

After motor 10 is set into operation with the current limiting resistors47 in circuit with the motor for a predetermined time interval duringthe'starting period, one of the motors 11, 12, may be set into operationby depressing the corresponding push buttons 34 or 35. When one of thepush. buttons 34 or 35 is depressed the switch 18 again is operated justprior to the connec tion of the corresponding motor to the supply linesso as to insert the current limiting resistors 47 in the motor circuitfor a predetermined time interval in exactly the same manner aspreviously described in connection with the starting of the motor 10. Ineach case the switch 18 responds when the push button disengages itsupper ment relay 19 serves to delay reclosure of the switch 18 and thusmaintains the short circuit around the current limiting resistors 47 enfor a predetermined time interval.

, sired limits and the resistor controlling switch .18 is returnedautomatically to its initial position a time intervalafter each motor isstarted. 7

With the selective switch 13 operated so as to energize the group ofmotors 10, 11, 12 from the low frequency supply lines L the operation ofthe motor controlling switch mechanism illustrated is exactly the sameas previously described exce t that the undervoltage protective relay 391s energized responsively to the voltage of the supply lines L and henceno further descrip: tion is necessary.'

' The motors 24, 25, may be set into operation at an time theundervoltage relay 39 is closed y depressing the COITQSPOILdHIg motorstarting push button 36 or 37. In each case the motor is connecteddirectly to the lowfrequency supply lines L since the motors are of sucha size as to not require limitation of the starting current thereof Aspreviously pointed out, any of the motors 10, 11, 12, 24, 25, which maybe in operation are stopped upon operating the normally closed stop pushbutton 38, while the motor 425 may be individually stopped by operatingthe normally closed stop push button 40 v v fWhile I have described andillustrated the preferred embodiment of vmy invention, it will beevident to those skilled in the art that various changes andmodifications may be. made therein without departing from the spirit ofthe invention or from ,the scope of the ap ended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. In amotor control system, the combination withv an electricmotor, of means including a switch operable from one position to asecond position 'for' connect ng the moto'rto a source of current uponoperation of said switch to said second ition and return thereof to thefirst pos1tion,-means for limiting the current of the motor, said meansnormally being inefiective, and means I set into operation uponoperationof said switch from said lone position for rendering. saidcurrent l1m1t1 means efiective prior to operation of sai switch to saidsecond position and" for a predetermined time 1nterval after the returnof said switch to said one 2. nationwith an electric motor, ofelectroosition. Y I I a-motor control system,-the COmbP responsivestartin switch mechanism for f hemot ea l m the current of the motorduring starting,'said means nor-,

mally being ineffective, a control switch current ofthe motor, anelectro time element circuit controlling device for I trolling switchto.said one position in accordance with its bias. 1 4

- 3. In a motor control system, the combination with an electric motor,of electroresponsive starting switch mechanism for connecting ,the motorto a source of supply, a control switch therefor operable from'onenected to eflfect operation of the electroposition to a second positionfor cheating 7,

operation of said starting switch mechamsni, a normally short, circuitedresistor in circuit with the motor, andiibrmally ener-' gized timeelemen electrbresponsive switch mechanism'under t e control of saidcontrol ,switch and arranged -to-vbe de-energized to remove the shortcircuit from, said resistor prior to the operation ofsaid startingswitch mechansim to start the motor and to maintain. the short circuitremoved from said resistor for a predetermined time interval A 4. In amotor 0 ntrol system, the combination with an electric" motorf-qfelectroresponsive line. switch, for connecting the mo'tor,to a source ofcufnent, a normally energized electr'oresponsive switch operable upondeenergization'thereof from an initial position to another position tolimit the current of the motor, a common control switch forsuccessively-deenergizingsaid current limiting switch and energizin saidline switch to start the motor wit limited current, and. time elementcircuit controlling meansset into operation under the control of saidcommon control switch for automatically efiecting the return of thecurrent controlling switch to-said position aftera timeinterval.

. 5. In a motor control system,--the combination with anelectricmotorgof an electroresponsive line switch for connecting themotor to a source'of current a normally energized electroresponaiveSWltCh operable upqn de-energization thereof from an-initial position tonsive all another position to-lir'nitj the u automatically controllingof said ,currentlimiting switch er oertain conditions, a masterf switchhaving two by said master switch and said time element device wherebythe said line switch is energized to connect the motor to a source ofcurrent after de-energization of the said current limiting switch toeffect operation thereof to said other osition and. the said currentlimiting switc gized to effect the return thereof to the said initialposition after a predetermined time interval.

6. In a motor control system, the combination with a plurality ofelectric motors having a common supply circuit, of a common currentlimiting means connected in the common supply circuit for the motors,switch mechanism for successively connecting the motors to said commonsupply circult, and cooperating switch mechanlsm and connections wherebythe said current limiting means is inserted in the supply circuit wheneach motor is connected thereto.

7. In a motor control system, the combination with a plurality ofelectric motors having a common supply circuit, of a separate switch forconnecting each motor to said common supply circuit, a normally shortcircuited current limiting resistance connected in the common supplycircuit for the motors, and electrore'sponsive circuit controlling meansjointly controlled by said separate switches and arranged to open theshort circuit around said resistance prior to the connection of eachmotor to the common upply circuit.

8. In a motor control system, the combination with a plurality ofelectric motors,

of separately operable line switch mechanism for each motor separateoperating a means for each line switch, a common current limitingresistor connectedin the supply circuit for the motors, a normallyclosed electroresponsive switch for short circuitin said resistor beforeand during operation each motor, connections whereby the saidelectroresponsive switch is operated to the open position to insert saidresistor in the supply circuit of the motors upon operation of thecorresponding operating means of each of said line switches to start thecorresponding motor, and time element means set into operation upon eachopening of said is re-enerby upon operation of any master switch the Ihaving a common supply line, of a .current limiting resistance connectedin the supply line for the motors, a se arate electroresponsive lineswitch for eac motor, a separate master switch for controlling each lmeswitch, a normall closed electroresponsive switch for short circuitingthe said resistor, a time element circuit controlling device associatedwith said normally closed electroresponsive switch and arranged to beset into operation upon the operation of said switch'to the openposition, and connections jointly controlled by each master switch andsaid time element device whereby the said normall closedelectroresponsive switch'is operate to the open position upon operationofany master switch to effect operation of the corresponding motor lineswltch and is reclosed after a predetermined time interval.

11. In combination in a system of motor control, a plurality of electricmotor having a common supply circuit, selectively operable switch mecanism for connecting said motors to said common su ply circuit inasequence as determined by t e operation of said switch mechanism, acommon automatically operated acceleration controlling means connectedin the common supply circuit for said motors, and, connections betweensaid switch mechanism and said means necessitating that each of saidmotors be placed under the control of said means 'upon the connection ofthe motor to the common supply circuit.

12. In combination in a system of motor control, a plurality of electricmotors having a "common supply circuit, selectively operable switchmechanism'efi'ective to connect said motors to said common supplycircuit in an order determined by the order of operation thereof, acommon automatically operated acceleration controlling means con-'nected in the common supply circuit for said motors, and connectionsbetween said swltch mechamsm and said means requiring said means to be moperative cond1t1on pr1or to the connection of each motor to the commonsuppl circuit and necessitating that each of sai motors be placed underthe control of said means upon the connection of the motor to the commonsupply circuit.

In witness whereof I have hereunto set my hand this 5th da of August,1925.

, CLA E G. RUNNER.

